PHASE NOISE-REDUCTION AND PHOTOELECTRON ACCELERATION IN A HIGH-Q RF GUN

The phase noise and jitter characteristics of the laser and RF systems of a high-gradient X-band photoinjector have been measured experiment ally. The laser oscillator is a self-mode-locked titanium:sapphire sys tem operating at the 108th subharmonic of the RF gun. The X-band signa l is produced from the laser by a phase-locked dielectric resonance os cillator and amplified by a pulsed TWT and klystron, A comparison betw een the klystron and TWT amplifier phase noise and the fields excited in the RF gun demonstrates the filtering effect of the high-Q structur e, thus indicating that the RF gun can be used as a master oscillator and could be energized by either an RF oscillator, such as a magnetron , or a compact source, such as a cross-field amplifier. In particular, the RF gun can play the role of a pulsed RF clock to synchronize the photocathode laser system; direct drive of a synchronously mode-locked AlGaAs quantum well laser has been achieved using the X-band gun RF f ields. This novel, gigahertz repetition rate, laser system is being de veloped to replace the more conventional femtosecond Ti:Al2O3 system, Some advantages include pumping this laser with a stabilized current s ource instead of a costly, low-efficiency pump laser. Finally, dark cu rrent measurements and initial photoelectron measurements are reported .